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1. How do I know I'm ordering a tube that is matched?
2. I want matched quads. How do I order the right quantity of tubes?
3. Why do you match power tubes?
4. How are power tubes matched?
5. How accurate is your matching?
6. What does the Perfect Pair number mean on my matched power tubes from thetubestore.com?
7. Which of your power tubes have the Perfect Pair matching number?
8. Does my amplifier require matched power tubes?
9. What does it mean to "bias" the amplifier?
10. What about "early breakup" and "late breakup" power tubes that you see with other brands?
11. Can I use your power tubes in my Mesa Boogie, Fender, Marshall, etc. amplifier?
12. Do you match other tubes (for example, pre-amp tubes)?
1. How do I know I'm ordering a tube that is matched?
Only tubes found in the power tubes section are matched. When you place a matched type into the shopping basket, the Options column will say "Price is for a: matched pair". If the Options column is empty, the price is for a single tube.
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2. How do I order the right quantity of tubes?
Unlike all our other tubes, which are sold individually, common audio power tubes
are ordered two at a time. If you order two or more pairs, we send a matched quad unless you specify otherwise. If you order three pairs we send a matched sextet. If you would like to purchase a single power tube, just mention this in the Comments of your order. This table explains what your "Order
Quantity" should be when placing an order.
Power tube ordering information
| If you want to buy... |
Your order quantity in the shopping basket should be... |
You are actually buying this many tubes... |
| One matched pair |
1
|
2
|
| Matched quad |
2
|
4
|
| Three matched pairs |
3
|
6
|
| Two matched quads |
4
|
8
|
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3. Why do you match power tubes?
Many amplifiers are designed to require power tubes that have similar cathode current. Even tubes of the same type made at the same time will have variations in their cathode current, and this is why testing and matching is required. Please note that not every amp actually requires it - but it never hurts to have matched tubes. See this answer for more info about whether you need matched power tubes.
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4. How are power tubes matched?
Power tubes are paired up based on their current draw, or "plate current". Measuring plate current draw under operating conditions is generally considered to be the most accurate method for rating a power tube, and it is the method we use.
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5. How accurate is your matching?
We match tubes to be within 5% of measured plate current (that is, the tubes won't differ from each other by more than 5%, or 1 milliamp in 20). Despite what many people may say, this is about as accurate as power tubes can be matched. Tubes will always test differently from day to day because of fluctuations in the power supply and "drift" in the tube over time as it ages. When you consider that most electrical components in a modern amplifier are built with a tolerance of 10%, this is more than accurate enough. By contrast, common practice in the tube industry for the last fifty years has been to match power tubes to within 25%.
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6. What does the Perfect Pair number mean on my matched power tubes from thetubestore.com?
The Perfect Pair number is the actual "plate current" (see question 4) that we measured, using our digital matcher with a regulated power supply. You can use this number when ordering so that you won't have to re-bias your amp (more about bias later).
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7. Which of your power tubes have the Perfect Pair matching number?
We provide Perfect Pair matching on the most common audio power tubes: EL34 types, 6L6 types, 6V6 types, 6550 types, KT88 types, and EL84 types.
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8. Does my amplifier require matched power tubes?
The best answer to this question is to consult your owner's manual. Reissues of vintage amps sometimes have substantially different circuits than the original, so it's difficult to make broad statements. Home audio amplifiers do not require it as often as guitar amplifiers. In any case, as long as you are buying a Perfect Pair type from thetubestore.com, you will receive power tubes that are all matched to each other, as we always ship quads or sextets when multiple pairs are ordered.
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9. What does it mean to "bias" the amplifier?
Just like the idle of your car may need adjusting when a major change is done to the engine, new power tubes need their idle (the "bias") adjusted to make sure the amp sounds as good as possible. Some amps do this automatically, but many do not - particularly in the world of guitar amps.
Many tube amp owners are unaware of this simple regular service for their amp that will keep it sounding it's absolute best. The bias methods of amplifiers fall into several basic categories:
- fixed bias amplifiers (no bias adjustment potentiometer)
- cathode bias amplifiers
- adjustable bias amplifiers.
Each of these types is unique. Fixed bias amplifiers CAN'T be bias adjusted. These amps (for example, some Fender and Mesa Boogie models) use a fixed resistor to bias the tubes, not a bias pot, and are designed to run with tubes that have a specific current draw (see question 4) and should only use tubes that fall within a certain range. Fortunately, these amps are usually pretty forgiving and will work well with a pretty wide range of tubes. For the best results, specify the make and model of your amp in the "Comments" of your order and we will make sure you get the best tubes for your amp.
Cathode bias amplifiers shouldn't require any adjustments and will work with a wide range of tube plate currents, as the circuit is "self adjusting".
For adjustable bias amplifiers, the amp should be biased by a tech with experience with this procedure. It's not difficult, it doesn't take long, but if you don't know what you're doing you may hurt yourself (amps can give lethal electric shocks even when unplugged, and NO, we're not just saying that to scare you). Also, your amp may sound horrible or cause undue wear and tear on the tubes or power supply. Until you learn how to do it correctly by yourself, it's best to pay a technician a few dollars to do it for you.
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10. What about "early breakup" and "late breakup" power tubes that you see with
other brands?
One important aspect of this concept is to keep in mind that it only works in fixed bias amplifiers. For comparison to the Perfect Pair numbers, lower numbers have "early breakup" (distort more easily) and higher numbers have "late breakup" (distort less easily). You can specify this in the "Comments" section of your order, and we will make sure you get tubes that have the desired effect.
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11. Can I use your power tubes in my Mesa Boogie, Fender, Marshall, etc. amplifier?
Yes. We sell tubes from the same factories that provide tubes to amp manufacturers. Like original parts for most equipment in the world, they tend to charge extra for spares and so ordering tubes from us can save you quite a bit of money. For guitar amplifiers, telling us the make and model in the "Comments" of your order is enough for us to supply you with the right tubes. For home audio, nearly all amps can take the full range of current tube production. There are rare cases where certain tubes won't run in some home audio amps, and that's what our 90 day exchange policy is for.
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12. Do you match other tubes (for example, pre-amp tubes)?
Circuits that actually require matched pre-amp tubes are so uncommon that we only offer this service on an order by order basis. The price for pre-amp tube matching is $5 per tube and not refundable. Power tubes require matching because the way they amplify sound waves can create exceptionally bad sound if they are poorly matched, but pre-amp tubes generally aren't used this way and so matching them is unnecessary.
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